用于发送POST请求，可以发送各种POST参数、传送文件，返回结果、下载文件。
说明如下：
public static string HttpPost(OnHttpPostProgress onProgress, //上传或下载进度，不需要可以传NULLstring url, // 请求的URL地址Dictionary<string,string> post = null, //要发送的参数，可以发送键值对、数组、对象等复杂数据string toFile = null, //如果指定了一个路径，请求结果保存为文件，如果传NULL，直接返回查询结果string upFile = null, //要上传的文件，传NULL不上传文件string fileField=null //默认为upFile，即PHP接收时使用$_FILE['upFile']
);public static class HttpWeb{/// <summary>/// HTTP 进度事件/// </summary>/// <param name="bUpload">TRUE为上传进度，FALSE为下载进度</param>/// <param name="lFininsh">已完成大小</param>/// <param name="lTotal">总共大小</param>public delegate void OnHttpPostProgress(bool bUpload, long lFininsh, long lTotal);/// <summary>/// 发送Post请求/// </summary>/// <param name="onProgres">上传或下载进度改变时</param>/// <param name="url">URL地址</param>/// <param name="post">键值对,如果要发送数组，请参考："man[0][name]"=>"hexu"; "man[0][age]", "18"); "man[1][name]"=>"hexu"; "man[1][age]", "18");如果不发送数据，可以传NULL</param>/// <param name="toFile">结果保存至文件，如果为NULL，则直接返回结果</param>/// <param name="file">要发送的文件路径</param>/// <param name="fileField">文件上传字段名字</param>/// <returns></returns>public static string HttpPost(OnHttpPostProgress onProgress, string url, Dictionary<string, string> post = null, string toFile = null, string upFile = null, string fileField = null){string result = null;try{//FileStream ws = null;string boundary = "------------" + DateTime.Now.Ticks.ToString();byte[] tailBoundary = Encoding.UTF8.GetBytes("\r\n--" + boundary + "--");HttpWebRequest hwr = WebRequest.Create(url) as HttpWebRequest;hwr.Method = "POST";hwr.ContentType = "multipart/form-data;charset=utf-8;boundary=" + boundary;hwr.Proxy = null;hwr.ProtocolVersion = HttpVersion.Version10;hwr.KeepAlive = true;hwr.Timeout = -1;hwr.ReadWriteTimeout = -1;hwr.AllowWriteStreamBuffering = false;long fileSize = 0;StringBuilder sb = new StringBuilder();if (post != null){bool bFirst = true;foreach (var pam in post){if (bFirst)bFirst = false;elsesb.Append("\r\n");sb.Append("--");sb.Append(boundary);sb.Append("\r\n");sb.Append("Content-Disposition: form-data; name=\"");sb.Append(pam.Key);sb.Append("\"\r\n\r\n");sb.Append(pam.Value);}}if (!string.IsNullOrWhiteSpace(upFile)){FileInfo fi = new FileInfo(upFile);if (!fi.Exists)throw new Exception("File Not Found");fileSize = fi.Length;fi = null;if (fileField == null)fileField = "upFile";if ( post != null && post.Count > 0)sb.Append("\r\n");sb.Append("--");sb.Append(boundary);sb.Append("\r\n");sb.Append("Content-Disposition: form-data; name=\"");sb.Append(fileField);sb.Append("\"; filename=\"");sb.Append(Path.GetFileName(upFile));sb.Append("\"\r\n");string expName = Path.GetExtension(upFile);if ((string.Compare(expName, ".xls", true) == 0) || (string.Compare(expName, ".xlsx", true) == 0))sb.Append("Content-Type: application/vnd.ms-excel");elsesb.Append("Content-Type: application/octet-stream");sb.Append("\r\n\r\n");}byte[] partOne = Encoding.UTF8.GetBytes(sb.ToString());long totalSize = partOne.Length + fileSize + tailBoundary.Length;long progressSize = 0;hwr.ContentLength = totalSize;using (Stream pstStream = hwr.GetRequestStream()){DateTime dtLastInvoke = DateTime.MinValue;pstStream.Write(partOne, 0, partOne.Length);progressSize += partOne.LongLength;if (onProgress != null){dtLastInvoke = DateTime.Now;onProgress.BeginInvoke(true, progressSize, totalSize, null, null);}if (fileSize > 0){using (FileStream fs = new FileStream(upFile, FileMode.Open, FileAccess.Read)){using (BinaryReader br = new BinaryReader(fs)){byte[] buffers = new byte[4096];int size = br.Read(buffers, 0, 4096);while (size > 0){pstStream.Write(buffers, 0, size);progressSize += size;if (onProgress != null){DateTime dtNow = DateTime.Now;if (dtNow.Subtract(dtLastInvoke).TotalMilliseconds >= 500){dtLastInvoke = dtNow;onProgress.BeginInvoke(true, progressSize, totalSize, null, null);}}size = br.Read(buffers, 0, 4096);}br.Close();}fs.Close();}}pstStream.Write(tailBoundary, 0, tailBoundary.Length);pstStream.Flush();pstStream.Close();if (onProgress != null)onProgress.BeginInvoke(true, progressSize, totalSize, null, null);}using (HttpWebResponse response = hwr.GetResponse() as HttpWebResponse){totalSize = response.ContentLength;progressSize = 0;DateTime dtLastInvoke = DateTime.Now;using (Stream resStream = response.GetResponseStream()){if (string.IsNullOrWhiteSpace(toFile)){using (StreamReader sr = new StreamReader(resStream)){StringBuilder sbr = new StringBuilder();char[] buff = new char[1024];int size = sr.Read(buff, 0, 1024);while (size > 0){for (int i = 0; i < size; ++i)sbr.Append(buff[i]);progressSize += size;if (onProgress != null){DateTime dtNow = DateTime.Now;if (dtNow.Subtract(dtLastInvoke).TotalMilliseconds >= 500){dtLastInvoke = dtNow;onProgress.BeginInvoke(false, progressSize, totalSize, null, null);}}size = sr.Read(buff, 0, 1024);}sr.Close();result = sbr.ToString();}}else{using (BinaryReader sr = new BinaryReader(resStream)){using (FileStream ws = new FileStream(toFile, FileMode.Create, FileAccess.ReadWrite)){int size = 0;byte[] buff = new byte[1024];size = sr.Read(buff, 0, 1024);while (size > 0){ws.Write(buff, 0, size);progressSize += size;if (onProgress != null){DateTime dtNow = DateTime.Now;if (dtNow.Subtract(dtLastInvoke).TotalMilliseconds >= 500){dtLastInvoke = dtNow;onProgress.BeginInvoke(false, progressSize, totalSize, null, null);}}size = sr.Read(buff, 0, 1024);}ws.Close();}sr.Close();result = "success";}}}}if (onProgress != null){onProgress.BeginInvoke(false, progressSize, totalSize, null, null);}}catch (Exception e){result = e.Message;}return result;}}